R. B. Clark

Plant genotype differences in the uptake, translocation, accumulation, and use of mineral elements required for plant growth

Plant genotypes differ in their uptake, translocation, accumulation, and use of mineral elements. Examples of genotype differences to iron, nitrogen, phosphorus, potassium, calcium, magnesium, manganese, boron, copper, zinc, and molybdenum are discussed. Current knowledge is sufficient to indicate that many crop plants can be improved for the efficient use of mineral elements and better adaptation to mineral stress conditions.

Effects of species of VA-mycorrhizal fungi on growth and mineral uptake of sorghum at different temperatures

Sorghum [Sorghum bicolor (L.) Moench] plants were grown in growth chambers at 20, 25 and 30°C in a low P Typic Argiudoll (3.65 µg P g−1 soil, pH 8.3) inoculated with Glomus fasciculatum, Glomus intraradices, and Glomus macrocarpum to determine effects of vesicular-arbuscular mycorrhizal fungi (VAMF) species on plant growth and mineral nutrient uptake. Sorghum root colonization by VAMF and plant responses to Glomus species were temperature dependent. G. macrocarpum colonized sorghum roots best and enhanced plant growth and mineral uptake considerably more than the other VAMF species, especially at 30°C. G. fasciculatum enhanced shoot growth at 20 and 25°C, and mineral uptake only at 20°C. G. intraradices depressed shoot growth and mineral uptake at 30°C. G. macrocarpum enhanced shoot P, K, and Zn at all temperatures, and Fe at 25 and 30°C above that which could be accounted for by increased biomass. Sorghum plant growth responses to colonization by VAMF species may need to be evaluated at different temperatures to optimize beneficial effects.

Benefit and cost analysis and phosphorus efficiency of VA mycorrhizal fungi colonizations with sorghum ( Sorghum bicolor ) genotypes grown at varied phosphorus levels

Sorghum [Sorghum bicolor (L.) Moench] was grown in a greenhouse in a low P (3.6 mg kg-1) soil (Typic Argiudolls) inoculated with the vesicular-arbuscular mycorrhizal fungi (VMAF) Glomus fasciculatum and P added at 0, 12.5, 25.0, and 37.5 mg kg-1 soil to determine the effects of VAMF-root associations on plant growth, benefit and cost analysis, and P efficiency (dry matter produced/unit P absorbed). Root colonization with VAMF and shoot growth enhancements decreased with increased soil P applications. Mycorrhizal plants were less P efficient than nonmycorrhizal plants. Shoot dry matter differences between mycorrhizal and nonmycorrhizal plants were considered the benefit derived by plants from VAMF-root associations. Shoot dry matter differences between mycorrhizal and nonmycorrhizal plants with similar P concentrations were considered the costs paid by plants for VAMF-root associations. Values of benefit and cost analysis for VAMF-root associations were highest when soil P was lowest and decreased with increasing P applications. Genotypic differences for calculated costs were pronounced, but not benefits. Benefit and cost analysis.may be helpful to evaluate host plant genotypes and VAMF species to optimize efficiencies of VAMF symbiosis in different soil environments.

Nitrate and ammonium uptake and solution pH changes for Al-tolerant and Al-sensitive sorghum (Sorghum bicolor) genotypes grown with and without aluminium

Plant tolerance to Al toxicity has been associated with differential nitrate and ammonium uptake and solution pH changes. Sorghum [Sorghum bicolor (L.) Moench] genotypes with tolerance (SC283) and sensitivity (ICA-Nataima) to Al toxicity were grown with different nitrate/ammonium ratios (39:1, 9:1, and 3:1) at 0 and 300 μM Al to determine genotypic differences in nitrate and ammonium uptake, changes in nutrient solution pH, and relationships of these traits to Al toxicity tolerance in the genotypes. ICA-Nataima had greater reductions in nitrate and ammonium uptake than SC283 when plants were grown with Al, but SC283 had higher nitrate and ICA-Nataima had higher ammonium uptake when plants were grown without Al. Differences in nitrate and ammonium uptake were associated with changes in solution pH; pH decreased as long as ammonium was in solution and increased when ammonium was depleted from solution. Greater changes in solution pH occurred when plants were grown with 39:1 compared to 9:1 and 3:1 nitrate/ammonium ratios. Solution pH values were lower when plants were grown with than without Al. The genotypes maintained their relative differences in Al toxicity tolerance when plants were grown separately or together in the same container with Al and with different nitrate/ammonium ratios.

Growth and yield traits of sorghum grown on acid soil at varied aluminum saturations

Genetic manipulation of crops to tolerate mineral stresses is a practical approach to improve productivity of tropical acid soils. Both acid soil tolerant (AS-T) and susceptible (AS-S) sorghum [Sorghum bicolor (L.) Moench] genotypes were grown in the field on an acid ultisol at Quilichao, Colombia, South America at 60% (60-Al) and 40% (40-Al) Al saturation to evaluate plants for growth and yield traits.Except for days to flowering and root mass scores, AS-T genotypes showed no differences in growth (plant height, head length and width, second internode length and diameter, and acid soil toxicity rating) and yield (total and stover dry matter yields, grain yield, head yield, seeds per head, and 100-seed weight) traits when plants were grown at 60-Al or 40-Al. Plants grown at 60-Al were delayed in flowering and had lower root mass scores. The AS-S genotypes showed improvement for the growth and yield traits when grown at 40-Al compared to 60-Al. The growth and yield traits of the AS-S genotypes were usually less favorable for plants grown at 40-Al than the same traits were for the AS-T genotypes grown at 60-Al. Harvest indices (ratio of grain to total plant yield) were no different for the genotypes grown at 40-Al, and only slightly higher for the AS-T genotypes grown at 60-Al. Sorghum genotypes more tolerant to acid soil conditions showed favorable growth and yield traits when grown under relatively severe acid soil (60-Al, pH 4.1) conditions. Certain sorghum genotypes were able to adapt and effectively produce grain when grown on acid soils with few inputs to reduce acid soil toxicity problems.

Effects of soil temperature on root and shoot growth traits and iron deficiency chlorosis in sorghum genotypes grown on a low iron calcareous soil

Iron deficiency chlorosis (FeDC) is a common disorder for sorghum [Sorghum bicolor (L.) Moench] grown on alkaline calcareous soils. Four sorghum genotypes were grown in growth chambers on a low Fe (1.3 μg/g DTPA-extractable), alkaline (pH 8.0), calcareous (3.87% CaCO3 equivalent) Aridic Haplustoll to determine effects of different soil temperatures (12, 17, 22 and 27°C at a constant 27°C air temperature) on various root and shoot growth traits and development of FeDC. As soil temperature increased, leaf chlorosis became more severe, and shoot and root dry weights, root lengths, and leaf areas increased markedly. Shoot/root ratios, shoot weight/root length, leaf area/shoot weight and leaf area/root weight and root length also increased while root length/root weight decreased as soil temperature increased. Severe FeDC developed in all genotypes even though genotypes had previously shown different degrees of resistance to FeDC. Genotypes differed in most growth traits, especially dry matter yields, root lengths, and leaf areas, but most traits did not appear to be related to genotype resistance to FeDC. The most FeDC resistant genotype had the slowest growth rate and this may be a mechanism for its greater resistance to FeDC.

Copper as essential to wheat reproduction

SummaryThe role of Cu in promoting the reproductive phase of growth was examined using Thatcher spring wheat (Triticum aestivum L.). Plants were grown in limed Bladen soil (pH 5.3) in a controlled growth room. The plants were first harvested when five leaves had developed (day 23) and some top leaves of Cu-deficient (-Cu) plants had rolled (withertip) indicating a Cu deficiency. The leaves were shorter on Cu than Cu-sufficient (+Cu) plants, and fewer leaves developed. As they entered the reproductive growth phase, +Cu plants accumulated reducing sugars and reduced 2, 3, 5- triphenyltetrazolium chloride (TTC) in their stems, while Cu plants had lower concentration of the reducing sugars and very little TTC was reduced indicating a reduction in energy and in reducing capacity. Thin-layer-chromatography showed that top leaves of Cu plants contained higher concentrations of aspartic acid, alanine, and serine; and less aminobutyric acid than +Cu plants. Nitrate, P, and K concentrations were higher, and Ca and Cu were lower in Cu than in +Cu plants.

Effects of silicon on growth and mineral composition of sorghum (Sorghum Bicolor) grown with toxic levels of aluminium

Silicon has been reported to alleviate some mineral toxicities in plants. Growth chamber studies were conducted to assess the effects of Si on alleviating growth reductions and nutrient imbalances in sorghum [Sorghum bicolor (L.) Moench] grown in nutrient solutions with toxic levels of Al. Treatments were 0, 300, 450, and 600 μM Al at 0, 1780, and 3560 μM Si. Increased levels of Al reduced shoot and root dry matter yields and total root length. Silicon in the growth medium enabled plants to overcome Al toxicity symptoms and enhanced shoot and root growth. Toxic Al levels decreased contents of all nutrient elements, especially Mg, Ca, Cu, and Zn, and decreased translocation of P from roots to shoots. Silicon counteracted many deleterious effects of Al on nutrient balances. Silicon apparently enhanced absorption of nutrients by enabling sorghum plants to maintain a higher root mass (root length) when grown with toxic levels of Al.

Organic acid and free proline accumulation and nitrate reductase activity in sorghum (Sorghum bicolor) genotypes differing in aluminium tolerance

Possible mechanisms for Al toxicity tolerance in plants involve complexation of Al by organic acids and other compounds and with activities of some enzymes. Al-tolerant (SC283) and Al-sensitive (ICA- Nataima) sorghum [Sorghum bicolor (L.) Moench] genotypes were grown with 0, 300, 450, and 600 μM Al to determine differences between genotypes for organic acids, free proline, and nitrate reductase activity (NRA). Organic acid concentrations in SC283 increased and remained relatively constant in ICA-Nataima, and roots showed greater changes than leaves when plants were grown with Al. Increases in oxalic, citric, and total acids in leaves of SC283 and t-aconitic and succinic acids in leaves of ICA-Nataima were noted with increased Al in solution. Increases in oxalic, citric and total acids in roots of SC283 and glycolic acid in roots of ICA-Nataima were noted as Al in solution increased. Contents of free proline in leaves and roots of both genotypes were not affected as Al in solution increased, but higher root proline concentrations in ICA-Nataima was believed to be an indirect or secondary effect of Al level. SC283 had higher leaf NRA than ICA-Nataima when plants were grown with Al. Enhanced organic acids and NRA might have been associated with Al toxicity tolerance in the sorghum genotypes, but proline accumulation did not appear to be.

Leaf mineral element concentrations in sorghum (Sorghum bicolor) hybrids and their parents grown at varied aluminium saturations on an Ultisol

Information is limited on genotypic differences for and genetic control of mineral element composition in sorghum [Sorghum bicolor (L.) Moench] grown on acid soils. This study was conducted to better understand variability of Al, N, Mg, Si, P, S, K, Ca, Mn, Fe, and Zn concentrations in 40 sorghum hybrids and their 14 parents grown in the field on an Ultisol (Typic Palehumult) in Colombia, South America. Both male and female parents and hybrids grown at 67 and 43% Al saturations differed extensively in mineral element concentrations. Significant male and female effects on the hybrids were found for most mineral elements. Male × female effects were rarely significant. Significant differences between parents and hybrids were observed for N, Mg, Si, Ca, Mn, Fe, and Zn at 67% Al saturation, and for Al, Si, and Ca at 43% Al saturation.